Structure for protecting scale graduations

Abstract

In a structure for protecting scale graduations, in which a graduation unit formed on a scale base is protected by a scale cover arranged on the top surface side of the graduation unit, a space between the scale base and the scale cover along the entire lateral periphery of the graduation unit is sealed using an adhesive agent mixed with a powder material such as a glass powder for blocking penetration of graduations-deteriorating components, to form a periphery adhesive layer. The scale cover may be supported on the scale base by a height regulating unit provided along the periphery of the graduation unit, so that variations in encoder output due to unevenness in thickness of the adhesive agent for joining the scale cover with the graduation unit can be prevented.

What is claimed is: 
     
       1. A structure for protecting scale graduations in which a graduation unit formed on a scale base is protected by a scale cover arranged on a top surface side thereof, wherein
 a space between the scale base and the scale cover along an entire lateral periphery of the graduation unit is sealed using an adhesive agent mixed with a powder material blocking penetration of graduations-deteriorating components. 
 
     
     
       2. The structure for protecting scale graduations according to  claim 1 , wherein the powder material is glass, ceramic or metal. 
     
     
       3. The structure for protecting scale graduations according to  claim 1 , wherein the powder material is transparent or nontransparent. 
     
     
       4. The structure for protecting scale graduations according to  claim 1 , wherein the powder material has a globular shape or an amorphous shape. 
     
     
       5. The structure for protecting scale graduations according to  claim 1 , wherein the powder material has a particle diameter of several nm to several μm. 
     
     
       6. The structure for protecting scale graduations according to  claim 1 , wherein a space between an upper surface portion of the graduation unit and the scale cover is also sealed using an adhesive agent. 
     
     
       7. A structure for protecting scale graduations in which a graduation unit formed on a scale base is protected by a scale cover arranged on a top surface side thereof, wherein
 the scale cover is supported on the scale base by a height regulating unit provided along a periphery of the graduation unit. 
 
     
     
       8. The structure for protecting scale graduations according to  claim 7 , wherein:
 the height regulating unit is formed on a lower surface of the scale cover in advance to have a pattern corresponding to the periphery of the graduation unit, and a lower end of the height regulating unit is allowed to abut against a top surface of the scale base; and 
 the scale base and the scale cover are joined with each other using an adhesive agent provided along the periphery of the height regulating unit. 
 
     
     
       9. The structure for protecting scale graduations according to  claim 7 , wherein the height regulating unit is deposited on the lower surface of the scale cover. 
     
     
       10. The structure for protecting scale graduations according to  claim 7 , wherein the height regulating unit is formed to have the same thickness continuously on the lower surface of the scale cover at a position corresponding to the entire periphery of the graduation unit. 
     
     
       11. The structure for protecting scale graduations according to  claim 7 , wherein the graduation unit has a thickness of 100 nm to 30 μm, and the height regulating unit has such a thickness that allows a space between the cover glass and the graduation unit to be 30 nm to 0.1 mm. 
     
     
       12. The structure for protecting scale graduations according to  claim 7 , wherein the height regulating unit is formed from metal including chromium, copper or aluminum. 
     
     
       13. The structure for protecting scale graduations according to  claim 7 , wherein the height regulating unit is deposited from the same material as that of the gradation unit. 
     
     
       14. The structure for protecting scale graduations according to  claim 7 , wherein a space between the scale base and the scale cover along an entire lateral periphery of the graduation unit is sealed using an adhesive agent mixed with a powder material blocking penetration of graduations-deteriorating components.